188 Putnam — Results of Pendulum Observations. 





Latitude 

 north. 



Longi- 

 tude w. of 

 Greenw. 



Eleva- 

 tion. 



g ob- 

 served. 



g reduced to 

 sea level. 



g com- 

 puted. 



Residuals, g re- 

 duced minus g com- 

 puted. 



Station. 



Bouguer's 

 reduction. 



Faye's 

 reduc- 

 tion. 



Bouguer's 

 reduction. 



Faye's 

 reduc- 

 tion 



Austin. Texas (Capitol) 



Austin, Texas (University) 

 Laredo. Texas 



3°0 16 30 

 30 17 11 

 27 30 29 

 29 18 12 

 29 56 58 

 4f> 11 11 



97 44 16 

 97 44 14 

 99 31 12 

 94 47 29 

 90 ©4 14 

 67 16 54 



meters 



170 



189 



129 



3 



2 



38 



dynes 

 979-274 

 979-269 

 979-068 

 979-258 

 979-310 

 980-618 



dynes 

 979-307 

 979-306 

 979-095 

 979-259 

 979-311 

 980-626 



dynes 

 979-333 

 979-332 

 979-109 

 979259 

 979-311 

 980632 



dynes 

 979-369 

 979-370 

 979-160 

 979-294 

 979 344 

 980-647 



dynes 

 -•062 

 -•064 

 -•065 

 -•035 

 -•033 

 — •021 



dynes 



— •036 

 -•038 



— •051 



Galveston, Texas 



New Orleans, La. 



Calais, Maine 



-•035 

 -033 

 — •015 













The continuation of the investigation of the question of 

 reduction to sea level and of the anomalies of gravity is essen- 

 tial to a satisfactory application of pendulum observations in 

 geodesy. The four stations in the south are of interest in this 

 connection as well as from a geological point of view because 

 of their comparative location. Two, Austin and Laredo, are 

 situated toward the interior about 150 and 135 miles (241 and 

 217 kilometers) respectively from the Gulf coast, and in a 

 region of erosion. Galveston is on a sandy island close to the 

 main land, from which it is separated by a bay into which 

 empty some small rivers. New Orleans is on the banks of the 

 Mississippi in the midst of the vast alluvial region built up by 

 that river, but is about 85 miles (137 km.) from the present 

 mouth of the river. Galveston and New Orleans are about 

 equally distant (nearly 100 miles or 161 km.) from the 100 

 fathom (183 meter) curve in the Gulf of Mexico, beyond 

 which line the water depths rapidly increase. It has been 

 estimated that an area of about 1,800,000 square miles is 

 drained by the Mississippi, Rio Grande and neighboring rivers 

 emptying into the Gulf of Mexico from the north, and that the 

 enormous amount of sediment carried by these rivers is depos- 

 ited within an area of 300,000 square miles along the northern 

 part of the Gulf.* If this added load accumulating for ages 

 and displacing sea water of only about one-third its density, 

 were sustained by a rigid earth, it would seem that there must 

 be an effect on the force of gravity measured at the surface 

 which would be quite within the range of observation, and 

 gravity in the loaded region would be found greater than 

 normal. If, on the other hand, there existed a perfect condition 

 of equilibrium, and an area so loaded continually adjusted 

 itself and sank in proportion to the load, in accordance with 

 the theory of isostasy, we would expect to find the force of 

 gravity quite normal. Should there be a lag between cause 



* These drainage and deposition areas are shown in the map, here reproduced, 

 with the author's permission, from -Mr. McGee's paper, later referred to. The 

 positions of the gravity stations are also shown. 



